Micro-fluid ejection devices such as ink jet printers continue to experience wide acceptance as economical replacements for laser printers. Micro-fluid ejection devices also are finding wide application in other fields such as in the medical, chemical, and mechanical fields. As the capabilities of micro-fluid ejection devices are increased to provide higher ejection rates, the ejection heads, which are the primary components of micro-fluid devices, continue to evolve and become more complex.
For example, higher resistance heater materials may be required in order to provide relatively large micro-fluid ejection head substrates so as to achieve faster fluid ejection speeds while using lower driving currents and lower nucleation energies. Higher resistance heater materials may also be required in order to provide ejection heads having less sensitivity to parasitic resistance thereby providing more consistent ejection droplet amounts. Accordingly, there continues to be a need for improved heater materials for micro-fluid ejection heads that can provide higher resistance, especially those that have greater bulk resistance and sheet resistance uniformity and a lower temperature coefficient of resistivity (TCR).
In one of the disclosed exemplary embodiments, a micro-fluid ejection head is provided that has relatively high resistance thin film heaters. The thin film heaters are made of silicon, metal and carbon (SiMC wherein M is a metal, such as chromium). The thin film heaters have a sheet resistance ranging from about 100 to about 600 ohms per square, and the SiMC thin film material of the heaters has a thickness ranging from about 100 to about 800 Angstroms.
In another exemplary embodiment, there is provided a method for making a micro-fluid ejection head, such as one for a micro-fluid ejection device. The method includes depositing a thin film material comprising silicon, metal and carbon (SiMC wherein M is a metal such as chromium) adjacent to a surface of a substrate to form a thin film resistive layer. The thin film resistive layer has a sheet resistance ranging from about 100 to about 600 ohms per square, a thickness ranging from about 100 to about 800 Angstroms, and a bulk resistivity ranging from about 300 to about 4000 μohm·cm. Anode and cathode conductors are defined adjacent to the thin film resistive layer to provide thin film heaters.
An advantage of the exemplary embodiments is that they may provide improved micro-fluid ejection heads having thermal ejection heaters that have lower energy requirements and less sensitivity to parasitic resistance. The heater resistors described herein may also have increased resistance which, for example, enables the resistors to be driven with smaller drive transistors, thereby reducing the substrate area required for active devices to drive the heater resistors. A reduction in the area required for active devices to drive the heaters enables the use of a smaller substrate, thereby reducing the cost of the ejection heads.